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CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  Institut  Canadian  de  microreproductions  historiques 

1980 


Tdchnical  Notes  /  Notes  techniques 


The  Institute  has  attempted  to  obtain  the  best 
original  copy  available  for  filming.  Physical 
features  of  this  copy  which  may  alter  any  of  the 
images  in  the  reproduction  are  checked  below. 


L'Institut  a  microfilm^  le  meilleur  exemplaire 
qu'il  lui  a  6t6  possible  de  se  procurer.  Certains 
ddfauts  susceptibtes  de  nuire  d  la  qualitd  de  la 
reproduction  sont  not6s  ci-dessous. 


D 


Coloured  covers/ 
Couvertures  de  couleur 


D 


Coloured  pages/ 
Pages  de  couleur 


D 
D 


Coloured  maps/ 

Cartes  g^ographiques  en  couleur 


Pages  discoloured,  stained  or  foxed/ 
Pages  d^colordes,  tachetdes  ou  piqu6es 


Tight  binding  (may  cause  shadows  or 
distortion  along  interior  margin)/ 
Reliure  serrd  (peut  causer  de  I'ombre  ou 
de  la  distortion  le  long  de  la  marge 
intdrieure) 


n 


Coloured  plates/ 
Planches  en  couleur 


Show  through/ 
Transparence 


Pages  damaged/ 
Pages  endommagdes 


D 


Additional  comments/ 
Commentaires  suppldmentaires 


Bibliographic  Notes  /  Notes  bibliographiques 


n 

D 
D 
D 


Only  edition  available/ 
Seule  Edition  disponrble 


Bound  with  other  material/ 
Relid  avec  d'autres  documents 


Cover  title  missing/ 

Le  titre  de  couverture  manque 


Plates  missing/ 

Des  planches  manquent 


Additional  comments/ 
Commentaires  suppl6r\.„..idires 


n 


Pagination  incorrect/ 
Erreurs  de  pagination 


Pages  missing/ 

Des  pages  manquent 


Maps  missing/ 

Des  cartes  g^ographiques  manquent 


The  images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legibility 
of  the  original  copy  and  in  keeping  with  the 
filming  contract  specifications. 


Les  images  suivantes  ont  6t6  reproduites  avec  le 
plus  grand  soin,  compte  tenu  de  la  condition  et 
de  la  nettetd  de  I'exemplaire  filmd,  et  en 
conformity  avec  les  conditions  du  contrat  de 
filmage. 


The  last  recorded  frame  on  each  microfiche  shall 
contain  the  symbol  —^(meaning  CONTINUED"), 
or  the  symbol  V  (meaning  "END"),  whichever 
applies. 


Un  des  symboles  suivants  apparaitra  sur  la  der- 
nidre  image  de  chaque  microfiche,  selon  le  cas: 
le  symbole  — ^>  signifie  "A  SUIVRE",  le  symbole 
V  signifie  "FIN". 


The  original  copy  was  borrowed  from,  and 
filmed  with,  the  kind  consent  of  the  following 
institution: 

National  Library  of  Canada 


L'exemplaire  film6  fut  reproduit  grdce  d  la 
gin6rosit6  de  I'dtablissement  prdteur 
suivant  : 

Bibliothdque  nationale  du  Canada 


Maps  or  plates  too  large  to  be  entirely  included 
in  one  exposure  are  filmed  beginning  in  the 
upper  Inft  hand  corner,  left  to  right  and  top  to 
bottom,  as  many  frames  as  required.  The 
following  diagrams  illustrate  the  method: 


Les  cartes  ou  les  planches  trop  grandes  pour  dtre 
reproduites  en  un  seul  cliche  sont  filmdes  d 
partir  de  Tangle  supdrieure  gauche,  de  gauche  d 
droite  et  de  haut  en  bas,  en  prenant  le  nombre 
d'images  n^cessaire.  Le  diagramme  suivant 
illustre  la  mdthode  : 


1 

2 

3 

1 

2 

3 

4 

5 

6 

■   J 

v 


BULLETIN   OF  THE  GEOLOGICAL  SOCIETY   OF  AMERICA 

Vol.  2,  pp.  125-140. 


THE  NICKEL  AND  COPPER  DEPOSITS  OF  SUDBURY 

DISTRICT,  CANxVDA 


HY 


UOBEUT  BELL,  B.  A.  SC,  ^l.  D.,  LL.  D. 

ASSISTANT    DIRECTOR   OF   THE   UEOLOGK'AI.   SURVEY    OF    CANADA 


With  an  Appendix  on 


THE  SILICIFIED  GLASS-BRECCIA  OF  VERMILION  RIVER,  SUDBURY 

DISTRICT 


uv 


GEORGE  H.  WILLIAMS 


ROCHESTER 

PUBLISHED  BY  THE  SOCIETY 

Fkhruary,   1891 


) 


BULLETIN  OF  THE  GEOLOGICAL  SOCIETY  OF  AMERICA 
Vol.  2,  pp.  125-140  February  5,  I89i 


THE   NICKEL   AND   COPPER   DEPOSITS  OF  SUDBURY 

DISTRICT,  CANADA. 

BY    UOBEKT    BELI-,   B.  A.  SC,    M.  D.,    LL.  P.,    ASSFST.VNT    DIRKCTOU   OF 
THE   GEOLOGICAL   hUUVEY    OF   CANADA. 

With  an  Appendix  on 

THE  SILICIFIED  GLASS-BRECCIA  OP  VERMILION  RIVER,  SUDBURY 

DISTRICT. 

BY   (JEOUOE   ir.    WriJ.IAMS. 
{Read  before  theSocieiy  December  31,  1890.) 

CONTENTS. 

Page. 

Introduction 125 

The  Ge()l(>!j;y  of  the  District 126 

The  Ores  find  their  A^isociiitions 131 

Mode  of  Occurrence  t)f  tlie  Ores 133 

The  Genesis  of  the  Ores 135 

Extent  and  Associations  of  the  Ores 130 

The  Silieified  Glass-Breccia  of  Vermilion  River,  Sudbury  District 138 


Introduction. 

The  town  of  Sudhnry,  a  creation  of  the  CanacHan  Pacific  railway,  is  situ- 
ated in  the  backwoods  of  Ontario,  thirty-six  miles  north  of  the  nioutii  of 
French  river,  on  Lake  Huron.  Parts  of  the  surrounding  country  are  tol- 
erably level,  but  in  a  general  way  this  region  may  be  said  to  be  hilly.  Some 
sections  are  very  broken  and  rugged,  whilG  in  others  rocky  ridges  alternate 
with  swamps  or  alluvial  intervals.  Occasional  tracts  of  land  are  fit  for  cul- 
tivation, but,  as  a  rule,  where  the  surface  does  not  consist  of  rock  or  swamp 
it  is  much  encumbered  with  bowlders.  At  one  time  the  district  supported 
large  quantities  of  white-pine  tin)l)er,  but  forest  fires  at  different  periods  have 
destroyed  the  greater  part  of  it  and  inferior  kinds  of  wood  are  now  growing 

XIX— UiH.L.  GKiir..  Hoc.  Am.,  Voi,.  2,  18i)().  ('-'"*) 


12()         I!.    I'.KI.I. —  NICKKL    AN1»    Cori'Klt    DKroslTS   OK    SI  IHilllY. 

up  in  it«  place.  Kock  niiipio,  red  oak,  l)lack  bircli  and  other  hard  woods 
form  coni-ideraljle  groves  in  some  sections.  Tiie  general  elevation  of  this 
tract  is  pnjl)al)]y  between  800  and  1,000  feet  above  the  sea. 

The  construction  of  the  Canadian  Pacific  railway  In  1(S82  led  to  the  dis- 
covery of  nickel  and  copper,  besides  various  other  metals,  in  this  part  of  the 
province,  and  now  the  Sudbury  district  promises  to  become  of  great  impor- 
tance as  a  mining  region.  It  may  be  remarked  in  j)assing  that  Sudbury  is 
not  the  name  of  a  political  division  but  is  merely  a  convenient  <lesignatioii, 
in  connection  with  mining,  for  the  territory  lying  jjartly  in  the  district  of 
Nijjissing  and  partly  in  that  of  Algoma. 

The  Geology  of  the  Distkict. 

As  a  preliminary  to  the  proper  understanding  of  any  account  of  the  nickel 
and  copper  deposits  of  the  Sudbury  district,  some  remarks  on  the  geology  of 
the  region  will  be  necessary.  The  district  is  situated  in  the  course  of  the 
best  known  and  perhaps  the  longest  Huronian  belt  in  Canada.  Beginning 
in  the  west,  the  general  northerly  boundary  of  this  great  belt  commences 
at  the  promontory  of  Naniainse-i^  on  the  east  side  of  Lake  Superior  and 
runs  approxinuitely  parallel  to  the  shore  of  that  lake,  the  St.  AFary's  river 
and  the  north  shore  of  Lake  Huron  as  far  as  Spanish  river,  leaving  a  border 
of  Huronian  rockx  of  varying  width  between  the  water  and  the  Laurentian 
nucleus  to  the  north.  Near  Spanish  river  the  dividing  line  between  the  two 
systems  turns  inland  and  runs  northeasterly  nearly  to  Lake  Wahnapitie, 
whence  it  trends  northward  and  northwestward  till  it  gains  a  point  lying 
northeast  of  Michipicoten  on  Lake  Superior,  thus  almost  surrounding  a 
large  elliptical  area  of  Laurentian  rocks. 

The  boundary  between  the  Huronian  trough  and  the  Laurentian  system 
along  its  southea.stern  side  leaves  the  shore  of  Lake  Huron  at  Shibaonaning 
(*' Killarney  ")  and  runs  in  a  tolerably  direct  line  to  the  foot  of  Lake  Temis- 
caming  at  the  great  bend  of  Montreal  river,  and  thence  it  continues  in  a 
somewhat  zigzaging  course  nearly'  to  the  southern  end  of  Lake  Mistassini, 
'SoO  miles  due  north  of  Montreal,  or  a  total  distance  of  600  miles  from  the 
commencement  of  the  belt  on  Lake  Superior  in  a  geiieral  course,  or  700 
miles,  following  the  axis  of  the  trough.  Lake  Wahnapitsc  lies  at  the  upper 
extremity  of  the  contracted  portion  of  the  Huronian  belt  after  it  has  turneil 
northeastward  from  Lake  Huron,  but  beyond  it  these  rocks  spread  out 
widely  to  the  northward. 

Within  the  general  limits  of  the  Huronian  region  just  sketched,  we  llnd  a 
good  many  inliers  of  gneiss  and  red  (|uartz-syenite,  some  of  which  correspond 
with  Laurentian  types  of  these  rocks,  and  it  is  uncertain  whether  they  are 


*  Meaning,  little  Hliirgeon  ;  often  improperly  spelled  Mamiiinse. 


-  ■    -  ■ 


OCCIHKKNCK   ON    KAST    ((tAHT. 


:571 


fntm  wliicli  till-  iiiiininiiitli.  Iii<liiiii  clcpliiiiil,  iiinl  /•,'.  uniiiiihirux  Iiiive  Itet'ii  il«'rive«l. 
Tlif  .'^liiiiii)  is  \viiiiili.*iriilly  like  stiiiii'  of  tlic  iiiaiiiiiidtliH  in  my  nillfctioii,  luit  it  is 
narrower. 

"(Signed)  W.  H.ivi.  Dawkins." 

"  I'liii.ADiM.niiv,    Do:   lOlh,  ISS?. 

"  I  Iiavi'  lu'vcr  swii  a  tooth  wliicli  prt'seiitH  all  tlic  ix'ciiiiaritics  of  tills  one,  hiit 
oarii  of  its  ciiaractcrs  can  lie  fouini  separate  in  ditrtTt'iit  tcctii  of  the  inaiiiinoth. 
It  is  prohaltly  a  last  lifciiliioiis  molar  of  a  variety  lietwtHin  the  typiral  K.  I'liiiiii/i- 
/ii/(,i  ami  the  smooth-plateil  A',  ruliinilii. 

"  (Si;rne<l)  K.  I).  Coi-k." 


Klil)liiiK  cohniilii  of  Dr  Iliiirh  Fiilconer,  to  which  tlii.s  inohir  hclonj^'s, 
acx'onliiiu;  to  Professors  W.  Hoyd  Dawkins  ami  K.  J).  Cope,  iuw  heen  found 
oil  the  I'aciCic  coast  of  Alaska/'^     Kaleoner  only  knew  of  its  remains  in 


E^^ 


KiciHK  \.  —  Mi)hii-  <if  Elcjilins  mhiiiilti  fruiii  Lnmi  Itlaivl,  llml.'.on  Run.     ('.j  tmliiriil  size.) 

the  more  southern  of  the  United  States  and  Mexico;  hut  the  present 
discovery,  and  lliat  of  a  similar  molar,  near  l*Mmonton,  N.  W.  T.,  taken 
in  connection  with  its  occurrence  in  Alaska,  shows  that  its  range  in  North 
America  was  even  more  extensive  than  that  of  I'J.  j>rimi(jciiii(.'^.  ( 'onsider- 
iiif^  how  very  rare  the  discovery  of  elejihantine  remains  of  any  kind  has 
hitherto  heen  overall  that  trreat  jiortion  of  the  continent  hetween  Bering 
strait  and  the  vicinity  of  lake  Erie,  we  may  reasonahly  expect  that  among 


*  Hull. till  uf  the  t'.  S.  (ifol.  Siiivrv,  no.  Hi.  18!l2. 


128         It.    JJi:i-L — NICKKL    AND   COPPKIl    UEl'OSIT.S   OF   SUDBUKY. 

Ill  the  district  under  consideration  the  main  lino  of  the  Canadian  Pacific 
railway  crosses,  almost  at  rij^ht  angles,  the  narrowest  part  of  the  Huronian 
helt  proper,  which  has  here  a  width  of  only  about  twenty-four  miles.  The 
strike  is  therefore  northeast  and  southwest,  and  in  this  pinched  portion  of 
the  trough  the  rocks  on  the  opposite  sides  dip  at  high  angles  toward  the 
center.  Sudbury  Junction  is  situated  southeast  of  the  center  of  the  trough, 
and  from  it  the  Hault  Ste.  Alarie  branch  of  the  railway  runs  upon  the  gen- 
eral strike  of  the  Huronion  rocks  throughout  almost  its  entire  length.  At 
thirty-three  miles  northwest  of  Sudbury  Junction,  or  near  Geneva  lake,  the 
main  line  enters  upon  an  outlying  basin  of  stratified  Huronian  rocks  meas- 
uring eight  miles  in  width  on  the  railway  by  seventeen  in  length  from  north- 
east to  southwest,  and  having  a  long  point  running  westward  into  the  town- 
siiip  of  Craig.  This,  for  convenience,  may  be  called  the  Geneva  lake  outlier. 
At  the  southern  extremity  of  Onaping  lake,  a  few  miles  to  the  north  of  this 
outlier,  there  is  a  smaller  one,  measuring  only  three  miles  in  width  by  four 
in  length. 

Tlie  various  members  of  the  Huronian  system  in  the  Sudbury  district  are 
of  much  interest  in  connection  with  questions  relating  to  metamorphism  and 
the  origin  of  crystalline  rocks,  and  also  as  illustrations  of  the  general  char- 
acter of  the  system  in  this  part  of  Canada.  They  consist  principally  of  gray- 
wackes  and  (juart/ites,  various  forms  of  diorites,  quartz-diorites  and  horn- 
blende schists,  mica  schists,  diabases,  argillaceous  sandstones,  black  and 
drab  clay  slates,  together  with  volcanic  breccias,  in  addition  to  the  gneiss 
and  quartz-syenite  already  referred  to. 

The  rocks  which  occur  in  greatest  cjuantity  in  the  stratified  Huronian  belt 
between  lakes  Huron  and  Wahnapitie,  and  which  constitute  the  lowest 
members  of  the  series,  are  ([uartzose  graywackes  and  (piartzites,  with  occa- 
sionally a  little  felsite.  Thick  bands  of  quartzites,  mostly  very  light  in 
color  and  standing  at  high  angles,  form  the  conspicuous  range  of  La  Cloche 
mountains  overlooking  Lake  Huron  and  the  long  narrow  points  projecting 
into  that  lake  between  Spanish  river  and  Killaniey.  The  fact  that  this 
great  local  development  of  (juart/ites  happens  to  occur  at  the  most  accessible 
part  of  our  principal  Huronian  belt  has  given  rise  to  the  erroneous  notion 
that  the  Huronian  rocks  of  Camida  in  general  consist  mostly  of  these  rocks. 
The  quartzites  of  the  region  about  La  Cloche  appear  to  belong  to  three  or 
four  belts  which  double  around  in  a  synclinal  form,  and  are  thus  repeated 
within  com|)aratively  narrow  limits,  (^uartzite  constitutes  tiie  principal 
rock  all  around  Lake  Panache  and  along  the  lower  parts  of  Vermilion  and 
S[)anish  rivers,  but  further  to  the  northea.stward,  or  in  the  contracted  part 
of  the  belt  of  the  Sudbury  district,  the  corresponding  rocks,  with  a  greatly 
diminished  volume,  are  much  mixed  with  felsnathic  and  argillaceous  matter, 
constituting  massive  graywackes;  Avhile  still  further  on,  or  in  the  country 


f 

i 


i 


DIOKITK    INTHUSIOXS    1\    (iUAY WACKKS    AND    «iUAUT/ITKS.        120 

east  of  Lake  AViilinapitfe,  they  have  passed  almost  entirely  into  pure  argil- 
litcs,  which  are  there  very  extensively  <level()pe(l.  To  tiie  north  of  Lake 
Wahnapittu  the  tpiartzites  reappear  in  great  force.  On  the  opposite  or  north- 
western side  of  the  8udi)iiry  trough  this  series  is  represented  by  a  tliick 
hand  of  gray  quartzite,  which  appears  to  be  always  characterized  by  scattered 
j)ebble3  of  white  quartz,  but  it  is  insignificant  in  volume  compared  with  the 
(pKirtzites  and  graywackes  along  the  southeastern  side  of  the  trough. 

Jn  the  graywacke  and  quartzite  area  of  the  region  under  consideration  the 
crystalline  diorites  occur  as  numerous  intruded  masses,  varying  from  half  a 
mile  to  ten  miles  in  length.  They  are  of  various  forms,  but  their  greatest 
diameters  are  approximately  parallel  with  the  strike.  The  rock  is  generally 
of  a  dark  or  sea-geen  color  and  moderately  finely  crystalline.  Three  or  four 
of  these  masses  occur  around  Lake  Panache  and  nine  or  ten  to  the  north- 
east, between  this  lake  and  the  Canadian  Pacific  railway  line,  and  seven 
more  beyond  that  part  of  the  railway  between  Sudbury  and  Wahnapitce 
river.  About  a  dozen  small  diorite  areas  have  been  found  in  the  quartzite 
and  argillite  region  around  Pake  Wahnapitai.  Besides  these  massive  dio- 
rite ,  bands  of  obscurely  stratified  varieties  of  the  same  rocks,  of  (juartz- 
diorite  and  of  dioritic  and  hornblendic  schists  are  sometimes  associated  with 
the  quartzites  and  graywackes  in  the  townships  of  McKim  and  Denison,  in 
the  Geneva  lake  outlier,  along  Spanish  river  and  around  Lake  Wahnapitie. 
A  beautiful  and  very  coarsely  crystalline  hornblende  rock  occurs  near  the 
Dominion,  the  Stobie,  and  the  McConnell  mines  and  in  a  few  other  localities. 

Bands  of  compact  brown-weathering  dolomite,  generally  whitish  and  dove- 
colored,  occur  locally  in  the  graywacke  and  quartzit'O  series.  They  are  found 
in  considerable  volume  on  different  parts  of  Lake  Panache,  and  they  occur 
also  near  Lake  Huron  in  the  township  of  Rutherford,  on  La  Cloche  lake, 
on  Wahnapitie  river,  on  Geneva  lake,  and  near  Cartie  ■  station.  Similar 
dolomite  is  occasionally  found  as  patches  in  the  tiner-grained  syenite  or 
altered  graywacke. 

Two  long  and  remarkable  intrusions  of  diorite  of  a  gray  color  and  having 
a  coarser  texture  than  those  already  descril>ed  are  found  cutting  the  gneiss 
and  quartz-syenite  areas  of  this  region.  They  are  each  al)out  a  mile  wide 
in  the  middle.  Both  run  northeast  and  southwest,  or  parallel  to  the  general 
strike  of  the  stratified  portions  of  the  Huronian  rocks  nearest  to  them,  and 
diminish  to  narrow  jioints  at  the  extremities.  The  first  of  these  commences 
at  Wliitson  lake,  in  the  township  of  Blezard,  and  runs  southwestward  into 
Denison,  a  distance  of  twenty-tour  miles,  while  the  second  has  been  traced  from 
the  northeastern  part  of  Levack  for  about  eighteen  miles  southwestward. 
Most  of  the  heavier  deposits  of  iiickeliferous  ore,  so  far  discovered,  are  asso- 
ciated with  these  two  diorite  belts,  and  they  will  be  again  referred  to  in  this 
connection.     A  smaller  dioritic  intrusion,  apparently  of  the  same  class  as 


i 


i 


130         I!.    IJKI.I, — XK'KKL    AM)    COPrKH    DKl'OSITS    OK    Slhlil  IJY. 

tlioise  two  and  ninning  piinillt'l  witli  them,  is  found  in  the  northeastern  part 
of  tlie  township  of  Morgan. 

The  next  niend)er  of  the  series,  in  ascending  order,  is  the  most  remarkable 
of  all.  It  consists  of  a  thick  l)elt  of  nearly  black  volcanic  breccia,  which 
luis  been  traced  from  Vermilion  lake  nortiieastward  in  the  valley  of  Ver- 
milion river  to  beyond  the  latitude  of  Wahnapita'  lake.  It  is  a  compact 
silicious  rock,  with  conclioidal  fracture  and  consists  of  angular  fragments, 
mostly  small,  closely  crowded  together  and  flecked  with  irregular  angular 
white  spots.  These  Dr.  G.  H.  Williams  finds  to  consist  of  fragments  of 
pumice,  which,  while  retaining  their  structure,  are  completely  replaced  by  ; 

silica.  This  band  appears  to  be  several  thousand  feet  thick  and,  as  it  has 
resisted  denudation  well,  forms  an  elevated,  rougii  and  broken  country 
along  its  whole  extent.  f 

The  highest  rocks  of  the  series  in  this  district,  or  those  which  occupy  the 
center  of  the  trough,  are  made  up  of  evenly  bedded  ilrab  and  grtiy  argilla- 
ceous sandstones  or  graywackes,  interstratiKed  with  shaly  or  slaty  !)eits,  and 
overlain  at  the  sunnnit  by  black  slates.  As  these  rocks  dip  at  comparatively 
low  angles,  they  occu])y  a  greater  geographical  width  than  the  other  mem-  ^ 

bers  in  proportion  to  their  thickness,  which,  however,  must  be  very  consid- 
erable. 

Along  the  lower  part  of  Spanish  river,  above  and  i)elow  the  great  bend,  the 
Iluronian  belt  has  a  wider  spread  than  near  Sudbury  Junction  and  here  we 
find  a  consideraljle  development  of  rocks  associated  with  the  quartzites  which 
are  not  met  with  to  the  northeastward  in  the  district  under  consideration. 
Among  these  are,  soft  bluish-gray  satiny  sericitic  schist,  sometimes  ligniform, 
accompanied  by  nearly  l)lack  hornblendic  schist ;  coarse  and  llMe-graiiied 
glossy  green  and  greenish-gray  schist ;  silver-gray  line-grained  mica-schist, 
studded  with  crystals  of  staurolite  ;  hard  green  schist ;  dark-gray  clay-slate; 
fine-grained  greenish-gray  silicious  felsite ;  and  slaty  graywacke,  passing 
into  gneiss. 

Tiie  stratiiied  Huronian  rocks  and  also  the  gneiss  and  (piartz-syeiiite  of 
Sudbury  district  are  traversed  by  dikes  of  gray,  coarsely  crystalline  diabase, 
which  are  often  large  and  can  be  traced  for  considerable  distances.  Their 
commonest  course  is  about  west-northwest.  They  all  have  the  same  physical 
characters  and  appear  to  be  of  identical  composition.  The  sound,  fresh  rock 
is  extremely  tough,  but  the  ex[)osed  surfaces  disintegrate  easily  under  the 
weather  into  brown  crumbling  debris,  especially  along  tlu;  joint-planes  and 
at  their  angles.  The  outer  portions  of  the  masses  thus  separated  scale  off 
concentrically,  so  that  they  become  rounded  and  bowlder-like.     These  dikes,  J 

as  we  shall  show  further  on,  a[)parently  p'ay  an  important  part  in  the 
economic  geology  of  the  district. 

■f 


Tin;  OiiKs  and  tuvam  Assocfations. 


Refeniiiji  now  to  the  nickel  and  copper  ores  for  which  this  district  is  he- 
coining  Cninous,  it  may  he  remarked,  in  the  first  phice,  that  there  is  much 
iiniforniity  l)()th  as  to  the  characters  of  the  ores  themselves  and  the  condi- 
tions under  wliich  they  occur.  Yet  these  deposits  are  not  confined  to  the 
nndonhtod  Hiironian  rocks,  hut  are  ecjualiy  alxindant  within  the  gneiss  and 
tliuM't/.-syenite  areas.  They  may  be  said  to  he  connected  witii  a  certain  geo- 
graphical area  rather  than  with  a  single  geological  horizon.  In  other  words, 
it  woidtl  seem  as  if,  within  certain  limits,  the  ores  might  have  had  their  origin 
beneath  all  tlie  rocks  found  at  the  surface.  The  ore  consists  in  all  cases  of  a 
mixture  of  clialcopyrite  and  iiickeliferous  i)yrrhotite.  The  area  over  which 
this  ore  has  been  found  up  to  the  present  time  extends  from  the  Wallace 
mine,  on  Lake  Huron,  in  the  vicinity  of  La  Cloche,  northeastward  to  the 
north  side  of  Lake  Walinapitie,  a  distance  of  about  seventy  miles,  and  from 
the  southeastern  boundary  of  the  Pluroiiian  belt,  in  the  Sudbury  district, 
nortliwesfward  to  the  limits  of  the  (Jeneva  lake  outlier,  a  distance  of  about 
fifty  miles. 

It  is  rather  singular,  first,  that  pyrrhotite  should  exist  so  commonly  within 
this  region  as  compared  with  any  other  in  the  country,  and,  secondly,  that 
no  matter  in  m  hat  kind  of  rock  we  find  it  to  occur,  it  should  generally  be  nick- 
eliferous  to  an  economic  extent.  Although,  as  a  rule,  pyrrhotite,  wherever 
found,  contains  traces  of  nickel,  it  has  only  been  detected  in  commercial 
quantities  in  a  few  places  in  other  parts  of  the  world.*  The  investigations 
of  the  writer  in  the  Sudbury  district  have  shown  that  the  cond)ined  nickel 
and  copper  ore  is  found  on  or  near  certain  lines  of  contact  between  diorite, 
on  the  one  hand,  and  j.'ueiss  or  quartz-syenite  most  frequently  on  the  other, 
but  only  at  certain  points  on  these  lines.  As  no  circumstance  is  without  a 
cause,  we  may  look  for  some  reason  which  determines  the  concentration  of 
the  ore  at  one  place  more  than  another,  and  the  writer  believes  he  has  found 
the  reason  in  this  case  to  consist  in  the  intersection  of  the  ore-bearing  belts 
near  these  occurrences  either  by  one  of  the  diabase  dikes  above  described 
or  else  from  the  pinching  in  or  perhaps  from  a  transverse  disturbance  of 
the  belt. 

The  ore  seems  to  have  been  derived  in  all  ca^es  from  the  diorite,  but  for 
some  reason  the  proximity  of  the  gneiss  or  quartz-syenite  appears  to  be 
also  fiivorable  fi)r  the  production  of  the  large  deposits.  If  the  diorite 
flowed  out  originally  upon  the  nearly  horizontal  surface  of  the  other 
rock,  the  constituents  of  the  ore  which  it  contained  may  have  sought  the 


♦  Assays  Imve  renently  been  made  of  samples  of  pyrrhotite  from  near  Shreiber  and  Jiickfish  bay, 
Lake  Hiippnor,  Htid  from  the  coiinlies  of  Peterboro',  Hastings,  and  Laimrli,  in  Ontiirio,  none  of 
winch  yieUkMi  more  tliiiri  traoes  of  niokel. 


132 


R.    V,ELT. — NICKEr,    AND    COlM'KI!    DKPOSITS    OK    SUDBURY. 


U)\V('r  portiiMi  of  the  mass;  or  if  it  were  injected  between  tlie  j)reexi.stiiig 
rocks,  these  materials  may  have  been  impelled  to  the  sides. 

Ill  some  cases  the  belts  of  diorite  are  much  broken  up  and  disturbed  longi- 
tudinally, and  along  these  horizons  they  are  mixed  with  large  and  small 
fragments  of  other  rocks  showing  lines  of  volcanic  movement  during  their 
formation.  JCxamples  of  coarsely  itrecciated  diorite  of  this  kind  may  be 
seen  near  the  Dominion  mine,  the  Stobie  mine,  and  thence  southwestward  to 
beyond  the  Canadian  Pacific  railway,  at  the  Copper  Cliff,  the  Crean  or  Mc- 
Coiniell  and  the  V^ermilion  mines,  in  Denison,  at  Ross'  location  north  of 
Morgan  township,  in  the  northeastern  part  of  Lcvack  and  near  the  western 
end  of  JJannerman  lake.  This  condition  of  the  diorite  seems  liivorablc  for  the 
production  of  the  ore,  probably  on  account  of  the  physical  disturbance  which 
it  indicates.  The  lines  of  northeast  and  southwest  disturbance,  along  which 
successive  occuirences  of  the  ore  are  found,  cannot  always  be  traced  con- 
tinuously on  the  ground,  but  as  the  evidences  of  such  disturbances  make 
their  appearance  from  place  to  place  upon  these  lines,  and  as  geological 
breaks  are  apt  to  be  very  persistent,  we  nuiy  infer  that  they  are  continuous. 

The  first  of  the  two  long,  narrow  intrusions  of  gray  crystalline  diorite 
which  have  been  referre<l  to,  in  its  course  from  Whitson  lake  to  the  township 
of  Denison,  cuts  off  a  narrow  slice  all  along  the  southeastern  border  of  the 
tongue  of  gneiss  and  quartz-syenite  which  lies  in  the  middle  of  that  part  of 
the  lluronian  belt.  The  ore  deposits  of  the  Waddell,  Dominion,  Russell, 
Little  Stobie,  Murray,  McConnell  (in  Snider),  Lockerby  and  Mclntyre 
properties,  of  lot  10,  range  I,  of  Snider,  of  the  Crean  or  Mc(,'onnell  mine,  and 
of  the  "mineral  range"  of  Denison  appear  to  be  all  situateil  along  the  south- 
eastern side  of  this  diorite  intrusion,  or  in  its  course,  when  it  becomes  Harrow  ; 
while  those  of  the  Stobie  and  Frood  mines  and  the  other  occurrences  for  two 
miles  southwest  of  the  former,  of  the  Copper  Cliff  and  others  in  the  vicinity, 
of  the  Evans,  of  lot  12,  range  III,  of  Graham,  and  of  the  Vermilion  mine 
lie  along  the  southeastern  side  of  the  separated  slice  of  the  gneiss  and 
(piartz-syenite  range  just  referred  to,  and  mostly  within  the  diorite  belt 
which  skirts  it  on  that  side. 

The  north  wall  of  the  Co|)per  Cliff  mine  is  formed  of  felsite,  (juartzite,  and 
a  coarse  red  mixture  of  feldspar  anil  ([uartz,  besides  diorite  like  that  of  the 
south  wall  ;  but  the  ore  itself  is  invarial)iy  associated,  here  as  elsewhere,  with 
the  diorite.  Tlu!  JOvans  mine  is  situated  further  from  the  contact  of  llu; 
gneiss  than  any  of  the  others.  The  top  of  the  ridge  on  which  it  occurs  con- 
sists mostly  of  graywacke,  but  the  ore  is  accompanied  by  diorite  which  in 
])arts  passes  into  a  kind  of  soapstone  or  serpentine.  A  break  in  the  con- 
tinuity of  the  gneiss  and  ({uartz-syenite  ridgi;  runs  northwestward  across  it 
from  the  Copper  Cliff  to  tiie  McConnell  mine,  and  all  along  this  break  there 
are  evidences  of  the  existence  of  the  ore,  accompanied  by  crystalline  and 


:i 


STllUCTrUAL    IIKLATIOXS   OF    TirrC    ()I!K    BODIES. 


1 


DO 

•)0 


sclii.stose  (liorites  uiul  si  hrecciated  condition  of  the  f^iieiss  and  quartz-syenite. 
Tiio  Kvan.s  niino  ap|)eurs  to  be  connected  witii  a  continuation  of  this  breal^. 
A  nurnher  of  more  or  h'ss  proniisinj,'  occurrences  of  the  mixed  ore  have 
been  fnund  in  the  two  soutliern  ran<,a's  of  Deni.son,  in  Louise,  Lorr.',  Nairn, 
Ikhlwin,  Drury  and  Hyman,  and  further  north  in  Neelon  and  McKim.    All 


FiiiiiiK  l  —  Serlioii  of  hrcccidtr.d  Ore  ffum  Miirraii  Minr. 

tiie.se  are  a.ssociated  with  diorite.     In  some  instances  they  have  been  found 
to  be  connected  with  lines  of  fracture,  and  this  may  prove  to  be  so  in  all 
,^      cases.     The  discoveries  of  the  ore  which  have  been  nuide  to  the  west  of  Lake 
Wahnai)itre  are  also  in  diorite  in  the  vicinity  of  (juartz-syenite. 


MoDIC   OF    OCCUUUKNCE   OF   TIIIC    OUKS. 

The  various  occurrences  of  the  mixed  nickeliferous  pyrrhotite  and  chal- 
copyrite,  as  far  as  they  have  yet  been  opened  up,  all  resemble  each  other  .so 
closely  that  a  description  of  one  will  apply  to  all.  They  are  associated 
primarily  with  the  diorite  masses  which  conform  more  or  less  nearly  with 
the  general  .strike  of  the  otiier  rocks  of  the  ccmntry.  The  oldev  lines  of  frac- 
ture or  disturbance  are  also  approxinuitely  parallel  with  the  strike,  but  their 
planes  may  incline  at  dilferent  angles  from  the  local  dip.  The  ore-bodies 
take  the  form  of  .stock-works,  following  the  .lirection  of  these  ancient  faults. 
The  bodies  are  made  up  of  a  mixture  of  the  country  rock  and  the  sulphides 
in  the  shape  of  a  confused  nuiss  of  coarse  and  fine  fragments  of  the  former, 
while  the  ore  itself  constitutes  the  matrix  or  filling  between  them.     The  frag- 

X\   -lUlL.  (il-.nl..  Scir.   Am.,  V(II..   '2,   1811(1. 


134 


K.    15i:i.L — NICKEL    AND    COPPER    DEPOSITS   OF   SfDRrKY. 


nieiits  are  of  every  size,  from  mere  grains  to  that  of  nuts  and  small  an«l  large 
bowlders  and  even  great  horses.     Sometimes  the  smaller  pieces  are  packed         W 
so  closely  together  as  to  admit  of  the  addition  of  little  ore,  while  at  other  i 


1 
0 


fe'»! 


mm 


FiGiitK.  •^—Section  of  decvni  posed  Ore  from  Murray  Mine. 

times  the  interspaces  are  wide  and  allow  the  introduction  of  large  riuantities 
of  solid  ore.  The  chalcopyrite  generally  occurs  in  the  midst  of  the  pyrrhotite 
as  distinct  masses  of  irregular  form  (sometimes  quite  large),  or  as  streaks. 


J 


^^;^^^£l=ss 


Fkuhf.  a  — Hand  Hjuciincii  of  Ore  from  Utoliie  Mine. 


patches  and  spots;  hut  occasionally  the  two  sulphides  are  more  intimately 
mingled.     In  a  part  where  the  pyrrhotite  prevails,  an  included  fragment  of 


KKLATIONS   OF    I'VUIiiroTITl';    AND    CITAr/'OI'YUTTK. 


135 


the  country  rock  may  be  coated  with  chalcopyrite,  or  the  latter  may  lie  as 
a  hunch  l)et\veen  the  rocky  fragments,  and  vice  versa  as  to  the  other  sulphide. 
There  i;*  no  uniformity  In  their  mode  of  occurrence  with  re<rard  to  one  an- 
other, and  they  appear  to  have  been  introduced  anK^ig  the  fragments  of 
broken  country  rock  simultaneously  and  under  the  same  conditions.  The 
diiM'itic  wall-rocks  on  either  side  and  also  the  indiideil  i)i/\vl(lers  and  even  the 
smaller  fragments  are  often  thickly  impregnated  with  disseminated  grains, 
spots  and  patches  of  all  sizes,  !)oth  of  |)yrrliotite  and  chalcopyrite.  The.«e 
spots  of  ore  have  usually  rounded  outlines  in  cross-section  and  approach 
spherical  and  ovate  forms.  The  two  sulphides  may  occur  side  by  side  in  the 
same  isolated  kernels  or  amygdules;  but  just  as  frequently  the  latter  consist 
of  one  or  the  other  alone,  although  in  such  cases  the  same  rock-section  may 
contain  as  many  of  the  one  kind  as  the  other  and  all  indiscriminately  mingled 
together. 

Figure  1  represents  a  fresh  section  of  tlu;  brccciated  ore,  two  feet  high 
and  a  foot  and  a  half  wide,  as  exposed  at  the  northeastern  end  of  the  drift 
from  No.  4  shaft,  Murray  mine,  in  October,  1890,  the  shaded  part  being 
mostly  chalcopyrite  (with  some  pyrrhotite)  and  the  rest  fragments  of  diorite. 
The  shaded  spots  in  one  of  the  latter  on  the  right  side  are  included  patches 
of  the  ore.  Figure  2  represents  a  section  four  feet  high  and  three  feet  wide 
of  the  decomposed  ore  on  the  southwestern  side  of  the  railway  cutting  through 
the  mass  at  the  Murray  mine.  The  shaded  portion  is  the  gossan  with  some 
undecayed  pyrrhotite  and  chalco[)yrite,  the  rest  being  fragments  of  diorite. 
Figure  '•>  represents  a  hand  specimen  of  the  ore  from  t\\^  Stobie  mine.  It 
was  traced  directly  from  nature  and  reduce('.  to  one-half  the  linear  dimen- 
sions. The  portion  shaded  horizontally  sliovvs  pyrrhotite,  the  verti(uil  shad- 
ing chalcopyrite  and  the  dotted  areas  rounded  fragments  of  the  silicious 
country  rock. 

Numerous  analyses  of  the  ores  have  shown  that  the  nickel  is  confined  to 
the  ))yrrliotite,  in  which  it  is  present  in  the  proportion  of  about  1  to  o  per 
cent. ;  but  it  has  not  been  determined  whether  it  replaces  a  corresponding 
proportion  of  iron  uniformly  throughout  the  mass  or  exists  in  the  form  of 
dis.seminated  grains  of  ])olydymite.  This  mineral  occur,s  as  crystals,  plainly 
visible  in  some  of  the  ores  from  the  Worthiiigtoii  mine,  in  the  townsiiip  of 
Drury. 

TiiK   Gknksis  ok  TIIK  OllKS. 

The  ore  bodies  of  tin;  Sudbury  district  do  not  appear  to  have  been  accumu- 
lated like  ordinary  metalliferous  veins  from  mineral  matter  inaiiueous  solu- 
tion, but  to  bave  resulted  from  igneous  fusion.  The  fact  that  they  are  always 
associated  with  diorite,  which  has  been  left  in  its  present  positions  in  a  molten 
state,  points  in  this  direction.     As  the  diorite  and  the  8ul[)hides  fuse  at  about 


loO  Ji.    IJKM- NJCKKJ.    AM)    COlM'l^ll    DKI'C  t.SlTS    OF    SfDIU  i;V. 

the  same  temperature,  they  would  naturally  accompany  each  other  when  in 
the  Huid  condition.  The  bodies  of  molten  diorite,  being  large,  would  remain 
Huid  for  a  HufHcient  time  to  aHow  the  dilliised  sulphuretted  metals  to  gather 
themselves  together  at  certain  centers  by  their  mutual  attractions  and  by 
concretionary  action.  Jn  the  case  of  great  irrupted  masses  of  diorite,  the 
bodies  of  ore  which  had  formed  near  enough  to  the  solid  walls  cooled  and 
lodged  with  a  nnxture  of  the  broken  wall-rocks  where  we  now  find  them, 
while  larger  (puiutities,  remaining  tluid,  probably  sank  slowly  back  through 
the  liquid  diorite  to  unknown  depths.  The  causes  which,  at  a  subsequent 
time,  favored  the  production  of  transverse  dikes  probably  aided  in  determin- 
ing the  deposition  of  the  ore  near  certain  lines  rather  than  elsewhere. 

If  we  suppose  that  the  molten  sulphides  abstracted  themselves,  by  the  laws 
of  mutual  attraction,  from  the  general  mass  of  the  fluid  rock  and  got  together 
in  considerable  quantities  in  an  intinuitely  mingled  form,  the  two  kinds 
would  tend  by  the  same  laws  to  separate  themselves  from  one  auother,  like 
going  to  like,  just  as  salts  of  diflerent  kinds  will  separate  into  their  respective 
crystals  from  an  aqueous  solution,  because  there  is  analogous  action  between 
nii.xtures  li(iuefied  by  heat  and  by  solution  in  a  su[)ersaturated  menstruum. 
A  study  of  the  relations  of  the  pyrrhotite  and  chalcopyrite  to  each  other  in 
these  mixed  ores  and  of  the  ores  of  the  parent  rock  shows  that  this  view  is 
in  accordanc(>  with  the  facts,  and  that  it  is  probably  a  satisfactory  explana- 
tion of  the  phenomena.  Xo  theory  (jfaipieous  deposition  appears  to  account 
for  the  facts  in  connection  with  these  ore  bodies;  still  we  do  occasionally 
observe  limited  local  moditications  of  the  ore  which  may  have  been  due  to 
the  solvent  action  of  water  with  subsequent  precipitation  of  mineral  matters 
long  after  the  consolidation  of  the  mass.  This  is  more  particularly  the  case 
with  regard  to  the  chalcopyrite.  Crystals  of  quartz  and  of  the  felspars  and 
rarely  of  apatite  are  found  end)edded  in  the  ore. 

EXTKNT    AND   ASSOCIATIONS   OK    TIIK   OuKS. 

Other  metals,  including  gold,  i)latinum,  tin,  lead,  silver,  zinc  and  iron,  have 
been  found  in  the  Sudbury  district,  and  probably  some  of  them  may  prove 
to  exist  there  in  paying  quantities.  The  presence  of  a  considerable  })ropor- 
tion  of  nickel  in  the  ore  of  the  Wallace  mine,  on  the  shore  of  Lake  Huron 
and  in  the  strike  of  the  Sudbury  deposits,  was  ascertained  by  Dr.  Hunt 
more  than  forty  years  ago ;  yet  the  presence  of  this  metal  in  the  latter  does 
not  seem  to  have  been  suspected  for  a  considerable  time  after  they  had  been 
worked  for  copper  alone.  The  ifuronian  is  notably  a  copper-bearing  sys- 
tem. West  of  Sudbury,  in  the  great  belt  we  have  already  traced,  this  metal 
occurs  around  Hatchawana  bay,  north  of  Sault  Ste.  Marie,  at  Little  Tidke 
George  and  Echo  lake,  at  Huron  Copper  bay,  in  Wellington  and  Bruce  mines* 


ASSOrlATIOI)    OltK.S. 


137 


on  Thessalou  and  MissLssagui  rivers,  and  elsewhere.  To  the  northeastward  it 
has  been  found  on  botli  sides  of  Lake  Wahnapitie,  on  Teniaf^nuui  and  Lady 
]')velyn  hikes,  along  Montreal  and  liUmche  rivers,  on  the  watershed  east  of  the 
canoe  route  between  lakes  Teniiseaniiiig  and  Abbittibi,  and  finally  near  the 
southern  extremity  of  Lake  Mistassini.  The  search  for  this  metal  along 
the  Huronian  belt,  which  has  been  described  above  as  running  for  more  than 
000  miles,  is  only  in  its  infancy,  and  the  copper-mining  industry  may  some 
day  be  very  extensively  carried  on  in  various  parts  of  this,  as  yet,  almost 
unknown  section  of  Canada. 


THE  SILICIFIEI)  (1  LASS-BRECCIA    OF   VEL'MILTON  JiJVER, 

S  UDJi  Un  1 '  I)  IS  Tin  <  'T. 

IIY    (iKOIKJK    II.    WII.MAMS. 

(liidd  befiirr  llu-  S<ici</i/  J)i:ce)nl)t'r  :5I,  IHOO,  an  an  .l/ipnii/i.r  tn  the  ciiniiimnicafKni  on 
the  Nii-lii-l  uiid  llupper  Orex  of  SiuUmry  Diatricf,  Caniida,  by  Dr.  Ruberl  Hell.) 

Ann  iig  11  coiirtiderahlc!  series  of  rocks  from  tlio  Siidlxiry  <listrict  wliicli  I 
have  recently  had  tlie  pK'asure  of  inieroscopieally  examiiiiiiii-  for  Dr.  Robert 
Jiell,  of  the  Canadian  (}eoh)gical  Survey,  there  was  one  of  such  unusual 
petrographical  eliaracter  that  it  well  merits  a  special  description,  More- 
over, this  rock  is  not  merely  a  jietrographical  anomaly,  but  it  also  occuj)ies 
so  large  an  area  as  to  become  geologically  of  great  importance  as  a  member 
of  the  Sudbury  series. 

The  specimens  of  this  rock  examined  by  me  in  Dr.  Bell's  collection  bear 
the  label  "Lowest  fall  of  Onaping  river,  Sudbury,"  and  turn  out  to  be 
nothing  less  than  a  breccia  composed  of  sharply  angular  fragments  of  vol- 
canic glass  and  pumice,  which,  in  spite  of  almost  comi)lete  silicilicalion,  still 
preserve  every  detail  of  their  original  form  and  microlitic  tlow-stritcture  with 
a  distinctness  not  to  be  exceeded  by  the  most  recent  productions  of  this  kind. 

Such  porous  glassy  rocks  are  well  known  to  be  more  subject  than  any 
others  to  either  alteration  or  comi)lete  removal,  so  that  the  preservation  of 
this  glass-breccia  from  Iluronian  times  without  loss  of  its  original  char- 
acteristics  must  be  regarded  as  very  exceptional.  The  production  of  a  nuiss 
like  this  on  so  large  a  scale  in  any  geological  time  is  also  a  matter  worthy  of 
notice,  for  Dr.  l^ell  has  traced  it  as  a  wide  baud  for  over  forty  miles  without 
then  reaching  its  northern  limit. 

The  following  memoranda  on  the  occurrence  and  distribution  of  this 
ancient  glass-breccia  have  been  furnished  by  Dr.  Bell  and  nniy  best  be  given 
in  his  own  words  : 

"This  roiniirlvaliln  rocic  lies  aloiic;  tlio  northwestern  side  of  llio  IIun)niiui  ti'iiu<;h, 
haviii;;-  tlio  red  qiuirtz-syoiiite,  which  nisiy  be  LHureiitiiin,  on  its  north wt'stern  tlanlc 
and  l)eint;;  bounded  on  the  southeast  by  what  is  iiere  the  hiijhest  nioinbei'  of  the  series, 
whieli  consists  of  thick-bedded  daric  bhiisli-gray  arijiUaceous  sandstone,  full  of  clear 
grains  of  quartz  and  interstratitied  with  shaly  beds  of  the  same  color,  all  overlain  by 
black  slates.  Towards  its  southwestern  toruiination  the  breccia  itself  passes  into  a 
black  slaty  mass  holdiiiijj  nuiiiy  pebbles,  mostly  of  syenite. 

"  The  belt  runs  from  the  township  of  Trill  northeastward  aloiii;  tin;  northwestern 
side  of  \'ermiIion  river  to  a  point  opposit(!  Waluuipita>  laki;,  where  it  cuts  aci'oss  the 
river  and  ('ontinucs  on  northeastward  ;  but  its  limit  iti  that  direction  has  not  been 
accurately  ascertained  beyond  foity  miles  tVom   the  township  of  Trill.     In  tbi.-  town- 

(i;38) 


LOCATION   OF    TIIK   fiT.ASS-mjFrciA. 


1.19 


§  -hip  il  (\irnis  ii  slmrp  olljow  appsirontly  ijctUtiE;  nrouiid  an  anticlinnl  axis  aiul  runs  off 

to  tliL' ca^twiiril  "11  tlu>  ^mithorii  side  of  Verinilioii  lake;  hut  licre,  as  aliovc  stated,  it 
passf'S  into  a  shi  ;■  conghjuieratu  lioidiiig  pobhlc.'s  c>f  syonito.  In  tills  Coitii  it  is  traoe- 
ahU.'  ahoiit  ten  miles  more. 

"A  i;ii()J  8(!t'ti()n  of  tlio  typical  foi'in  of  tlio  hroccia  may  be  soon  in  tin;  ciittings  near 
Onajiinuj,  when'  llio  Canadian  I'acitio  railway  intersects  it,  twenty-three  miles  north- 
west of  Sudhury  Junction.  It  hr.s  an  average  breadth  of  fully  a  mile,  and  as  it  dips  at 
angles  of  4")°  and  iijiwards  it  must  have  a  thickness  of  over  4,000  feet.  Owing  to  its 
hardness  and  toughness  it  has  resisted  denudation  better  than  the  sandstones  and 
argillites,  and  it  rises  a  f(!W  hundred  feet  above  the  lattt^r  in  the  form  of  a  range  of 
rugged  hills  overlooking  the  comparatively  level  country  on  the  southeast.  Along  its 
northwestern  side  it  is  separated,  in  jdaees  at  least,  from  the  quartz  syenite  by  a 
massive  band  of  asli-gray  (juartzite  containing  usually  an  abundance  of  white  quartz 
pebbles  scattered  through  it. 

"  It  was  supposed  that  from  its  compact  nature  this  breccia  might  be  iis(;d  in  orna- 
mental (''instruction  ;  but,  while  it  gives  a  good,  smooth  surface,  it  has  not  been  found 
susceptible  of  fine  pidish." 

Ill  a  hand  .fpeciiiien  this  rock  presents  a  nearly  bhick  felsitie  matrix,  in 
which  are  enil)e(U!e(l  s-harply  angular  or  .slightly  rounded  fragments,  vary- 
ing from  Ij  em.  in  diameter  downwards  to  ultra-mieroseopie  dimensions. 
The.se  fragments  are  lighter  in  color  than  the  matrix,  hut  diHer  consideralilv 
among  them.selves  in  their  tint,  structure  and  composition.  The  majority 
resemble  chalcedony  in  appearance,  others  are  greenish,  while  some  of  the 
largest  fragments  are  now  replaced  hy  a  single  calcite  individual.  Occa- 
sional small  grains  of  clear  vitreous  (piartz  may  also  he  detected,  while  specks 
of  magnetic  pyrites  (pyrrhotite)  are  everywhere  al)undant.  Many  of  the 
angular  fragments  show  distinctly  under  the  lens  a  flow  or  vesicular  struc- 
ture, which  is  .still  more  apparent  in  a  thin  section  of  the  rock  when  seen 
under  the  micro.scope. 


Fkh'uk  i.—ScclidU  (if  .silicitud  GI<i.'<sDierria. 


The  appearance  of  this  rock  when  viewed  with  a  low  magnifying  power 
(X  -0  diameters)  is  shown  in  the  accompanying  figure  4,  for  which   I  am 


140 


O.    ir.    WILLIAMS — SILICIFI?:n   GLASS-BRECCIA. 


indebted  to  the  skill  of  Mr.  Charles  R.  Keyes,  Fellow  in  Geology  at  the 
Johns  Hopkins  University. 

The  fragments,  even  down  to  those  of  the  smallest  dimensions,  have  the 
angular  form  characteristic  of  glass  sherds  produced  by  explosive  eruptions. 
The  larger  fragnicnt  in  the  lower  part  of  the  figure  is  finely  vesicular,  while 
the  one  above  is  more  coarsely  so.  The  How  structure  is  as  perfectly  marked 
by  sinuous  lines  of  glcjbulitesand  microlites,  which  terminate  abruptly  against 
the  broken  edge  of  the  glass  particle,  as  in  the  most  recent  vitrophyre. 
Minute  spots  of  opaque  pyrrhotite  are  scattered  through  the  section.  The 
groundmass  is  of  a  dark  color,  owing  to  the  massing  in  it  of  minute  black 
globulites,  to  whose  nature  the  highest  magnifying  power  gives  iv^  clue. 

Unfortunately,  no  analysis  of  this  interesting  rock  has  as  yet  been  nuide. 
Between  crossed  Nicols  it  is  seen  to  be  made  up  largely  of  chalcedonic 
quartz,  which  has  changed  the  easily  destructible  glass  into  a  sort  of  jasper. 
Chlorite  is  also  abundant,  froijuentl^'  arranged  as  a  border  of  radiating 
scales  around  the  edges  of  the  fragments,  so  as  to  coat  them  green  in  the  hand 
specimen.  The  larger  grains  are  always  a  fine  mosaic  of  interlocking  (piartz, 
but  some  of  the  smaller  ones  are  composed  of  a  unit  individual  of  clear  vitre- 
ous quartz.  The  only  other  minerals  which  could  be  identified  in  the  sec- 
tion are  calcite  and  a  few  grains  of  a  glassy,  striated  feldspar.  The  presence 
of  this  latter  mineral  is  very  noteworthy,  as  we  should  expect  it  to  have  dis- 
appeared during  the  vicissitudes  through  which  this  rock  has  passed. 

After  a  careful  study  of  this  rock  I  find  it  possible  only  to  interpret  it 
as  a  remarkable  instance  of  a  very  ancicait  volcanic  glass-breccia,  preserved 
through  the  lucky  accident  of  silicification.  Nor  did  this  process  go  on,  as 
is  usual,  through  dentrification  and  loss  of  structure,  but  rather  like  the 
gradual  replacement  of  many  silicified  woods,  whose  every  minute  detail  of 
structure  is  preserved.  The  rarity  of  such  rocks  in  the  earth's  oldest  forma- 
tions is  readily  intelligible,  but  for  this  very  reason  the  exceptional  preser- 
vation of  a  rock  like  this  is  all  the  more  welcome  proof  that  exjjlosive 
volcanic  activity  took  place  at  the  surface,  then  as  now,  and  on  a  scale,  if 
possible,  even  greater  than  that  with  which  we  are  familiar. 


